Hydraulic system



Ml! 4 1948' R. a. sPRAGuE r-r A1. 2,441,040

mmunxc sYs'rnu rma Aug. 2, 1944 INVENTORS Robert B. Sprague Lewis- E'. erhelson Attorney Patented May 4, 1948 HYDRAULIC SYSTEM Robert B. Sprague, Long Beach, and Louis E. Berthelson, Los Angeles, Calif., assignors to North American Aviation, Inc.

Application August 2, 1944, Serial No. 547,803

9 Claims. l This invention relates to hydraulic systems and has as its general object to provide control mechanism which permits hydraulic pressure to be transmitted from either of two pressure creating sources to a common pressure actuated device. It has special application to hydraulic brake systems for vehicles such as aircraft wherein it is desirablel to permit control of the brakes from either of two pilots stations.

. A further object of the invention is toprovlde controlmechanism which permits two independent pressure creating devices to be operated f either singly or simultaneously and, under conditions of simultaneous operation, to transmit the force of only one ofthe devices, i. e., which prevents th'e simultaneously applied forces being added to each other in the effect upon the actuated device.

Another object of the invention is to provide in a hydraulic system of the type indicated, a control mechanism which, in response to pressures delivered from both of two independentlyr controlled pressure creating devices, will transmit to the actuated device the highest of such pressures and will prevent the transmission of the lower pressure.

More speciiic objects of the invention are to provide a control mechanism which is responsive to the higher of two sources o! pressure and which will transmit such higher pressure to. a

l common actuated device; to provide such a con- 4trol mechanism which is of relatively simple, in-

expensive and durable construction; to provide a control mechanism having two inlets and a single outlet and which is adapted to transmit pressure from one inlet to the outlet directly through a fluid column and to transmit fluid from the other inlet to the outlet by displacement. of a moving part ofthe control mechanism which separates the columns of iluid at the inlet and outlet of the control mechanism.

While the invention may be applied to various types of hydraulic systems, we have chosen an airplane hydraulic brake system for the purpose of illustrating one embodiment of the invention in the accompanying drawings, wherein:

Fig. lis a longitudinal sectional view through a control mechanism incorporating the invention, in the position in which it .transmits pressure from one of two alternative sources;

Fig. 2 is a longitudinal sectional view through the control mechanism shown in the position in which it transmits pressure from another source;

and

1 5 voir 4 through the supply linesl, 8 and 8'., andforce the fluid into the control mechanism B 2 Fig. 3 is a schematic showing of a hydraulic system incorporating the invention.

Referring first to Fig. 3, a hydraulic brake system incorporating the invention may include va. pair of yalternate sources of pressure A and A' fed from a reservoir 4 and. adapted` to transmit pressure, through the control mechanism B, to a set of actuated devices C and AC (such as hydraulic brakes) which are indicated schematically. The pressurel sources A and A' may be ofy any conventional type, either power-driven ,or-

manually-operated, the devices chosen for illustration being the. manually-operatedtype includv ing a cylinder Sand a Apiston therein operated by a. foot pedal 6, receiving fluid from the reseradapted, when the plungers are depressed, to

through the lines 9 and 9.

Referring now to Fig. 1, th'econtrol mechanism` B comprises a housing in two sections,` I0 and I I (to permit access tothe internal parts) threaded together as at I2. Within the section II) is defined a chamber I3 and inthe section II is a cylinder I4 which cooperates withthe chamber I3 to accommodate a. plunger I5. The. plunger I5 has a piston indicated generally at I6 and operating in the cylinder I4. The piston I6 comprises a pair of anges I1, Ila on the plunger I5, and an 0 ring I8 of compress'ible, resilient material such as neoprene, which is con'- fined between the anges I'I, Ila and engaged under compression againstl the wall of the cylinder I6. y

The plunger vI5 has a reduced shank portion I9 which is received in a cylinder 20 of reduced diameter in the casing Section Il. The cylinders I9 and 20 are Separated by a shoulder 2lagainst which the flange Ila is urged (by a coil spring 22) in order to dene one limit of movement of th'e plunger I5. In this position of the plunger I5, uid from the source A' will enter the control mechanism (as indicated between arrow 23) through the inlet 24, thence will pass through a bore 25 in the plunger I5 and past -a valve element 26 into an enlarged bore 25a (see Fig. 2), thence through a port 21 in the side of the plunger I5 and into the chamber I3, and

of a shoulder dened between the bores 25 andV 25a, but in the position shown in Fig. 1, the valve 26 is unseated by the engagement of its stem 30 l with the end of a set screw Vequalize between the 3l threaded through the end wall 32 of Ythe casing section Il. A light spring 33 urges the valve element toward seating position.

In the position of the control mechanism shown in Fig. 2, pressure is transmitted as indicated by the arrow 33 through the inlet 34 into a chamber 35 which is'deiined between the flange I'Ia and the shoulder 2i within the cylinder |45* Expanding the chamber 33,. the fluid forces the plunger I5 to the left as viewed in the drawing, compressing the spring 22, and placing the iluid in the chamber I3 under pressure. As soonas sumcient movement of the plunger I5 has occurred to move the stem out oi contact with the set screw 3l, the valve element 26 will seat under the combined action of the spring 33iand the pressure of fluid in the chamber I3 so as to prevent flow oi' fluid through' the bores 25a, 25 and thus the continued movement of the plunger to the left will force iluid out of the outlet 23 as indicated by the arrow 36.` v

When Apressure is applied to both inlets 24 and 34 simultaneously, the pressure at the inlet 34, if greater than that at the inlet 24, will overcome the pressure from the inlet 24 tending to open the valve 23, causing the valve 26 to close so as to cut oil? flow from the inlet 24 and only the pressure 4from the inlet 34 will be transferred to the outlet 28. Conversely, if the pressure at the inlet 24 is sufliciently greater it will overcome the combined pressure from the inlet 34 and the push of the light spring 38 tending to close the valve 26, resulting in the valve 26 being opened and the pressure being transmitted by fluid column through the bores 25, l25a and the chamber I3. Since the pressure in the chamber I3 will be transmitted in all directions, it-will react against the piston I6 in greater force than the pressure A acting against the piston IB from the inlet 34 and will therefore neutralize the latter pressure.

In either case, the pressure from either inlet is balanced against the pressure from the other inlet while being applied tol the outlet, and consequently only the higher pressure will be applied at the outlet. l

When pressure on the foot pedals is released thel back pressure in the brake lines will force the plunger I9 toward the right as viewed in the drawings, forcing the fluid from the chamber back out through the inlet 34 and forcing the iiuid from the chamber 20 back through the inlet 24. As the plunger nears the end of its retracting stroke, the stem 30 of the lvalve element will be stopped by the set screw 3| and further retracting movement of the plunger will cause the valve 26 to open ,and permit the pressure to ports 24 and 23 through the bores 25 and 25a;

The foregoing may be taken as illustrative of one form in which the invention may be embodied, -it being our intention to cover in our claims the use of any equivalent arrangement or apparatus.

We claim as our invention: v

1. For a hydraulic system including a `plurality of sources oi fluid pressure and^a common uid path for the transmission of pressure to an actuated device ordevices, a control mechanism operatively connected to said plurality of sources to receive pressure therefrom and to selectively e '4 moving part through mitted from the other of said sources to the nuid in the common path. 2. In combination with a hydraulic system including a plurality of sources of iluid pressure and a common nuld path for the transmission or iiuid pressure to an actuated device or devices, a control mechanism adapted to receive the fluid pressure from both of said sources and to deliver such pressure to said common path, said control mechanism including a continuous iiuid passageway extending from one ot said sources to said common path, a moving part through which pressure is transmitted from the other of said sources to the iiuid in the common path and' means responsive to pressure from the greater of said sources to equalize the pressure from any lesser source to thereby transmit pressure from the greater source to the common path.

3. A control mechanism as deined in claim 1, wherein said continuous fluid passageway comprises the bore of a hollow plunger which includes a, piston comprising said moving part, said bore communicating with one of said :duid pressure sources and said piston being subject to iluidA pressure from the other source.

4. A control mechanism as defined in claim 1, wherein said continuous iiuid passageway comprises the bore of a hollow plunger whichincludes a piston comprising said moving part, said bore communicatingwith one of said uid pressure sources and said piston being subject to pressure from the other of said iiuld pressure sources, and a valve in said bore adapted, when the fluid pressure against said piston is greater than that against the face of the. valve in said bore, to close said bore against the transmission of fluid therethrough, and, when the pressure against the 'valve in said bore is greater than that against of said inlets and an outlet chamber in communication with said outlet, said plunger having a bore and a valve for closing said bore, said bore being adapted, when said valve is open, to establish a iluid column from the other of said inlets to said outlet, said valve being adapted to close under pressure transmitted to said outlet chamber by said piston from said inlet chamber, when said last mentioned pressure is greater than that applied to said other inlet to said bore.

6. A control mechanism as dened in claim 5, wherein said casing provides a second inlet chainber of less diameter than said cylinder and separated therefrom by a shoulder against which said piston is adapted to abut to limit retracting movement of said plunger, and resilient means for yleldingly urging said plunger in 'the retracting direction, said shoulder deiining one ex- A tremity of said rst mentioned inlet chamber.

transmit the greater of suchlpressures to said common path, said control mechanism including a continuous uid passageway extending from one of said sources to said common path. and a 7. A control mechanism as dened in claim 5, wherein said casing provides a second inlet chamber of less diameter than said cylinder and separated therefrom by a shoulder against which said piston is adapted to abutto limit retracting movement of said plunger, and resilient means for yieldingly urging said plunger in the re-J tracting direction, said shoulder defining one extremity of said first mentioned inlet chamber,

which pressure is trans-l 5" said valve element having a stem adapted, in said retracted position of the plunger, to contact a fixed abutment carried by said casing, thereby to open said valve.

8J In combination with a hydraulic system including a plurality of sources of fluid under pressure and a common path rfor the transmission of fluid under pressure to an actuated device or devices, a control mechanism adapted to receive the fluid pressure from either or both of said sources, said control mechanism including means to transmit the uid pressure to the actuated de vice or devices from the one of said sources which `provides the higher pressure, means for maintaining separation between the fluid from said sources, and means responsive to release of lthe uid pressure at said sources to release fluid from said common path.

9. For a hydraulic system including a plurality oi sources of fluid pressure and a common fluid path for the transmission of pressure to an actuated device or devices, a control mechanism for selectively transmitting pressure from either 0f said plurality of sources to said common path including a part movable in response to pressure from one or said sources to thereby transmit pres sure to said common path, a passageway connecting another of said sources to said common path and means responsive to the pressure from the greater of said sources to equalize the pressure from any lesser source whereupon only pressure from the greater source will be transmitted to the common path. l

ROBERT B. SPRAGUE. LOUIS E. BERTHEION.

REFERENCES CITED The following references are ot record in the le of this patent:

UNITED STATES PATENTS Number Name Date 2,216,855 Sanford s Oct. 8, 1940 2,247,302 Lvy June 24, 194i 2,300,694 Overbeke Nov. 3,- 1942 2,312,686 Campbell Mar. 2, 1943 2,342,878 Maineri Feb. 29, 1944 

